The present invention relates to an electrical switch, also known as a snap switch. Such an electrical snap switch is designed for selectively establishing either a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. Typical electrical snap switches may include a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established. The electrical snap switch may further include a conductive unit which is fixed with respect to the housing and which includes first, second, and third conductive fixed contacts. The electrical snap switch may include a switching unit comprising a conductive swaying element, a first end of the conductive swaying element being pivotally engaged with the first conductive element, and the second end of the conductive swaying element being arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to the housing and a second end secured to the swaying element such that when the pushbutton is in the first pushbutton position, the spring is in a first spring position and the spring causes the swaying element to electrically connect the first and second conductive fixed contacts, and when the pushbutton is moved to the second pushbutton position, the spring is moved to a second spring position and the spring causes the swaying element to also move to electrically connect the first and third conductive fixed contacts,
An example of such a switch is disclosed in U.S. Pat. No. 7,205,496, the contents of which are hereby incorporated by reference, in which the spring is a helicoidally wounded traction spring and in which the pushbutton driving portion acts on the middle section of the spring. Due to this arrangement, an abrupt changeover of the switching unit occurs but it is not possible to obtain a quick changeover and, furthermore, the elastic behaviour of the spring is affected by its cooperation with the driving portion and the changeover point, or instant, varies and the switch is therefore not reliable. The same drawbacks are also inherent to the design disclosed in U.S. Pat. No. 4,636,597.
An attempt to improve the working of such a snap switch is illustrated in U.S. Pat. No. 6,255,611 in which the switching unit is bistable between first and second positions of the swaying element, in which the switch comprises a return spring which is disposed between the housing and the pushbutton, in which, when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring, and in which the traction spring has a first end connected to the driving portion of the pushbutton and a second end secured to the swaying element, so that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position, and when the pushbutton is moved to the second pushbutton position, the first end of the spring is moved to a second spring position.
According to such an arrangement, when an external force is applied to the pushbutton, the jointed end of the driving portion of the pushbutton and the elastic spring is forced to move downwards until it passes a critical line, at which point the swaying element is coupled with another conductive fixed contact to supply power or electrical signals.
However, the changeover speed remains insufficient and no solution is provided for a “double” or “twin” design for selectively establishing simultaneously two first conductive ways, each one between a first conductive fixed contact and a second conductive fixed contact. Similarly, there is no design that simultaneously provides two second conductive ways, each one between the first conductive fixed contact and a third conductive fixed contact.